It's probably Chrome that enabled the software renderer for users with unsupported GPU configurations. Note that the software renderer is extremely slow (it barely manages to and unsupported systems are more likely than not to have a weak CPU that further lowers performance. We're talking performance at a level barely enough to animate the cube at https://get.webgl.org/ . I don't know the value of that software renderer, other than making Chrome look better on statistics.
Neat. What happened in the summer of 2013?